'The work of the charity, as of its peers, is of great value. We listen to, and seek to understand, the assurances given by the Oxfam leadership.'

But a spokesman for Visa said the financial firm was talking to Oxfam to understand what had happened and what the response would be.

'We are committed to the highest standards of professional and personal conduct, and we expect the same from our partners,' the spokesman said.

An M&S spokesman said: 'These are very serious allegations. M&S continues to monitor the situation very closely as we seek to understand the steps that Oxfam is taking to address them and develop a robust safeguarding plan for the future.'

Former international development secretary Priti Patel (pictured) has led calls for Oxfam chief executive Mark Goldring to stand down

James Daunt, managing director of Waterstones, said the allegations were 'reprehensible and beyond comprehension'.

'It sounds as though what went on in Haiti betrays the fundamental values of Oxfam,' he added. 'The part we have worked with I have been impressed by, though that is not to excuse the utterly abhorrent behaviour in Haiti.

'I expect Oxfam to give a full and frank explanation, and if there is something to apologise for, to apologise.'

The Innocent drinks company, which gives Oxfam around £100,000 a year, said it wanted to see a clear plan 'for how this could not ever happen again'.

Richard Reed, the millionaire co-founder of the juice firm, said: 'As a corporate sponsor, we would want to see a very, very clear comprehensive plan for how this could not ever happen again.

'If these actions turn out to be true, then of course we would revisit the funding. Because you're giving money to do good. You're not giving money to do these other things.'

Heathrow Airport, which also has a corporate partnership with Oxfam, said: 'We are in touch with the charity and are taking this matter very seriously'

Heathrow Airport, which also has a corporate partnership with Oxfam, said: 'We are in touch with the charity and are taking this matter very seriously.'

The Co-operative Bank said: 'We are monitoring the situation closely.'

Three other major partners – Sainsbury's, Unilever and Accenture – did not respond to requests last night to issue public backing.

Mr Goldring has emailed corporate donors to say he felt 'great shame in the behaviour of those few who did not uphold Oxfam's or society's values'.

The revelations had been 'painful and shocking for Oxfam supporters around the world' but did not represent the charity', he wrote.

In just three days individual donors have withdrawn 1,270 direct debit instructions, Oxfam admitted yesterday.

The cancellations represented a possible loss of £12,039 a month, or £144,468 a year, based on the average monthly donation of £9.48.

Mark McElroy, 82, from Derby, told the Guardian: 'I have been a direct debit contributor for several years.

Oxfam's CEO Mark Goldring (left) has emailed corporate donors to say he felt 'great shame in the behaviour of those few who did not uphold Oxfam's or society's values'

'I am shocked that some of my donations have been used in the way it appears. If these allegations are not true then I shall reinstate the direct debit I cancelled today.'

One volunteer-led store, Belfast Books in Northern Ireland, tweeted to say: 'The directors of Belfast Books have unanimously decided to suspend all book donations to Oxfam until further notice.'

Earlier in the week it emerged that that not all Oxfam shop volunteers had received criminal record checks – and that the charity had received multiple allegations, including of abuse of children by volunteers.

A spokesman for the Duke of Edinburgh's Award said: 'The safety of participations is the DofE's biggest priority. In light of these allegations, we will be reviewing our association with Oxfam as a participant volunteering provider.'

'Heads of all organisations are ultimately responsible and accountable for the actions and inactions that happen which cause serious harm to others.

'This scandal has been mishandled from the start and Mark Goldring needs to step down so Oxfam can rebuild their reputation and focus on helping the poorest in the world. This is a defining moral issue, there can be no more excuses, we need accountability, justice and a voice for the victims now.'

Mr Goldring has refused to step down even after admitting he had not acted quickly enough when a whistle blower raised concerns about abuse.

Helen Evans, Oxfam's former head of safeguarding, accused her bosses and the Charity Commission of not doing enough when she revealed allegations that its workers had been involved in abuse.

Tory MP Nigel Evans, who is a member of the Commons international aid committee, said: 'Mark Goldring did not act quickly enough on the whistleblowing, and this has clearly led to more of it happening. If he agrees that he was slow in listening to the siren warnings from senior officers in his organisation, then he should go.'

Yesterday the chairman of the Oxfam board of trustees, which has the power to declare no confidence in the chief executive, gave Mr Goldring her backing.

Caroline Thomson told Sky News: 'I have complete confidence in Mark Goldring. He's doing a brilliant job and Oxfam's a wonderful organisation which is going through some difficult times.

'Haiti is a disgrace and we're very ashamed of what happened there but we're going to move on and continue to earn the support of the British public.'